Respiratory and excretory metabolism of fish fry of yellow-spotted grunt Plectorhynchus cinctus

Effect of environmental factors on the oxygen consumption and ammonia excretion of yellow-spotted grunt Plectorhynchus cinctus were determined. The results showed that the oxygen consumption of P. cinctus increased with the increase of stocking density, the relationship between oxygen consumption rate and stocking density can be expressed by Y=8.1304X－1.0512（R2=0.9879）. Ammonia excretion of P. cinctus showed the trend of hyperbola as stocking density increasing, relationship between ammonia excretion and stocking density can be expressed by Y=－0.0047X2+0.0542X+0.0776（R2=0.5806）. Oxygen consumption and ammonia excretion of P.cinctus decreased as its weight increasing. Relationship between body weight and oxygen consumption, ammonia excretion can be expressed by Y=2.163X－0.8495(R2=0.9273) and Y=0.2394X－1.0344 (R2=0.7794), respectively. Average oxygen consumption and ammonia excretion in day time were lower than that at night, oxygen consumption in valley bottom value being 89.19% of that of peak value and ammonia excretion in valley bottom value being only 22.01% of that of peak value. Routine oxygen consumption was 1.19~1.39 times higher than basal oxygen consumption, and routine ammonia excretion was 1.23~1.96 times higher than basal ammonia excretion.