Comparison of feeding and metabolism between black-shell strain andwild population of the Pacific oyster (Crassostrea gigas)

In order to clarify the physiological basis of fast growth traits of an excellent black-shell strain of the Pacific oyster (Crassostrea gigas), feeding and metabolism between the black-shell strain and wild population of C. gigas were compared. Results indicated that at the test temperature (16-32 °C), temperature had significant effects on clearance rate (CR), oxygen consumption rate (OCR) and ammonia excretion rate (AER) of C. gigas. With the increasing of temperature, the CR of the black shell strain of C. gigas began to rise, reached the maximum at 28 °C and then declined, while the CR of the wild population of C. gigas reached the maximum at 24 °C. The OCR and AER of black shell strain and wild population increased with temperature, no significant turning point was found. There were significant differences in CR and AER between black shell strain and wild population of C. gigas. The black shell strain had higher CR and lower OCR than wild population, and had significantly lower AER than wild population at 32 °C. At the test salinities of 15 to 35, salinity had significant effects on CR, OCR and AER of C. gigas. CR, OCR and AER of C. gigas increased firstly and then decreased with increasing salinity. There were significant differences in CR between the black shell strain and wild population of C. gigas. The black shell strain had higher CR than wild population, and its AER was lower than that of wild population in range of salinity 15 to 25. The O∶N ratio of C. gigas reached the maximum at 16 °C and salinity 35, increase in temperature or decrease in salinity reduced O∶N ratio. In the temperature experiment, the O∶N ratio of the black shell strain ranged from 10.52-29.31. In the salinity experiment, the O∶N ratio of the black shell strain ranged from 11.51-22.98. The present results demonstrated that the black shell strain of C. gigas could adapt to high temperature and low salinity environment, and selective breeding of black shell strain of C. gigas could produce oysters that have higher intake of energy and lower metabolic costs.