Growth performance, hematological and biochemical parameters, and hepatic antioxidant status of spotted knifejaw Oplegnathus punctatus in an offshore aquaculture net pen

Spotted knifejaw (Oplegnathus punctatus) is a promising species for aquaculture production because of its high commercial value and limited supply. The growth performance, hematological and biochemical parameters, and hepatic antioxidant status of spotted knifejaw reared in an offshore aquaculture net pen system (OANPS) were examined to evaluate the potential development of offshore fish farming on the north coast of China. Results showed that 50, 000 juveniles spotted knifejaw (initial mean body weight 392.73 +/- 58 g) were transferred to OANPS and had a survival rate of 98%, final mean body weight of 790.05 +/- 12.83 g, body weight gain of 101.2%, feed conversion ratio (FCR) of 1.52, and specific growth rate (SGR) of 0.59% d-1 after 120 days. The hepatosomatic and the viscerosomatic indices (HSI and VSI) of the spotted knifejaw did not change significantly. The plasma albumin and globulin contents of the spotted knifejaw reared in the OANPS increased significantly. In contrast, the plasma alkaline aminotransferase and aspartate aminotransferase activities significantly decreased at the end of the experiment. However, the plasma glucose, cholesterol, triglyceride contents and albumin/globulin levels, white blood and red blood cell numbers, hemoglobin, and hematocrit contents showed no significant differences throughout the experimental period. Hepatic superoxide dismutase and glutathione peroxidase activities were significantly increased, and the catalase activity and malondialdehyde levels remained unchanged. In addition, the low hepatic lipid droplet number was observed in the spotted knifejaw reared in the OANPS. These results indicated that juveniles spotted knifejaw reared in an OANPS can show a high survival rate and high growth performance and physiological status through short-term culture. The OANPS opens a new door for spotted knifejaw culture. These findings enhance our understanding of spotted knifejaw aquaculture and contribute to offshore fish farming in China.