Effects of salinity on the physiological responses of the large yellow croaker Pseudosciaena crocea under indoor culture conditions

The physiological responses to different environmental salinities were assessed in juveniles of large yellow croaker Pseudosciaena crocea. This species shows a good capacity to adapt to comparatively low environmental salinities by evaluating some physiological responses, i.e. superoxide dismutase (SOD), acid phosphatase (ACP), alkaline phosphatase (AKP) and lysozyme (LZM) in the liver, spleen, gill and kidney respectively. Growth and survival at salinity 5 parts per thousand, 10 parts per thousand and 25 parts per thousand were better than those at salinity 15 parts per thousand and 20 parts per thousand. No significant differences in ACP, AKP, SOD and LZM in the liver were observed among different salinity treatments; SOD, AKP and LZM in the spleen among different treatments only showed significant differences at the beginning or the 2nd week; in the gill, no significant difference of AKP and LZM were observed during the whole experiment, SOD among different treatments showed significant difference at the beginning and the 8th week, and ACP only showed significant difference at the end of the experiment; in the kidney, significant differences in ACP, AKP and SOD among different salinities were merely observed at the end of experiment, and LZM showed significant difference among different treatments at the 2nd week. Overall, some slight stress responses were observed, but few significant differences were observed between low salinity and normal salinity, especially the growth and physiological functions were not influenced by low salinity, i.e. 5 parts per thousand and 10 parts per thousand. We conclude that juvenile large yellow croaker is tolerant to low salinity and shows a potential for low salinity culture.